1. Field of the Invention
The present invention relates to an optical element, an optical module holder including the optical element, an optical module, and an optical connector. In particular, the present invention relates to an optical element, an optical module holder including the optical element, an optical module, and an optical connector that are suitable for forming an optical path system used to monitor light emitted from a light-emitting element.
2. Description of the Related Art
Use of an optical module including a light-emitting element, such as a vertical-cavity surface emitting laser (VCSEL), for reasons related to cost and stability is increasing in optical communication using optical fiber.
An optical module such as this couples light including communication information, emitted from a light-emitting element, with an end face of the optical fiber via a lens. As a result, the optical element is used to transmit communication information via the optical fiber.
Among optical modules, an optical module is used in which a light-receiving element, in addition to the light-emitting element, is included within a package (CAN package) to support bi-directional communication. The light-receiving element receives light including communication information that has been carried via the optical fiber and emitted from the end face of the optical fiber.
Light output characteristics of the light-emitting element used in an optical module such as this change due to effects caused by temperature and the like. To stabilize output characteristics, the light (particularly the amount of light) emitted from the light-emitting element is preferably monitored.
Technologies described in Patent Literature 1 and Patent Literature 2, for example, have been known as conventional technology related to a light-emitting element including a specific structure used to acquire light for monitoring from the light-emitting element.
In other words, a following invention is disclosed in Patent Literature 1. In the invention, a mirror is disposed between an optical fiber and a surface emitting laser. A portion of light-emission output from the surface emitting laser is reflected to a light-receiving element side. The light receiving element receives the reflected light. As a result, the light-emission output from the light-reflecting element is monitored.
A following invention is disclosed in Patent Literature 2. A portion of light emitted from a light-emitting element and transmitted within an optical fiber is reflected by a semitransparent mirror to a light-receiving element side. The light-receiving element receives the reflected light. As a result, the light-emission output from the light-reflecting element is monitored. The semitransparent mirror may be configured by a filter composed of, for example, a dielectric multilayer. In this case, the semitransparent layer is separate from the lens.
In addition, for example, in an optical module 1 shown in FIG. 9, a CAN-package type photoelectric conversion element 4 is attached to a photoelectric conversion element attaching section 3 of an optical module holder 2. The photoelectric conversion element 4 includes a surface emitting laser 5, a monitoring detector 6, and a glass window 7. The surface emitting laser 5 serves as a light-emitting element. The monitoring detector 6 serves as a light-receiving element. The glass window 7 is at an angle to a center axis of light emitted form the surface emitting laser 5. In an optical module 1 such as this, a portion of light emitted from the surface emitting laser 5 is reflected by the glass window 7. The monitor detector 6 receives the reflected light. As a result, the light emitted from the surface emitting laser 5 can be monitored.    [Patent Literature 1] U.S. Pat. No. 6,607,309    [Patent Literature 2] Japanese Patent Laid-open Publication No. 2001-343559
However, the above-described conventional technologies have problems such as those described below.
In other words, in the conventional technologies disclosed in Patent Literature 1 and Patent Literature 2, the mirror or the semitransparent mirror disposed between a light transmission line and a light-emitting element is separate from the lens. Therefore, manufacturing procedures during assembly and the like may become complicated. Cost may increase because of the increase in the number of components. Furthermore, optical characteristics may deteriorate when a highly precise positioning of the mirror and the lens cannot be performed during assembly.
When the semitransparent mirror configured by the filter composed of the dielectric multilayer is used, increases in the complexity of the manufacturing procedures and in cost are expected because of a film-forming procedure.
It is thought that the above-described CAN-package type photoelectric conversion element including the glass window 7 has difficulty supporting high-speed optical communication of 10 Gbps or more. This is because crosstalk sometimes occurs in a CAN-package type photoelectric conversion element 4 such as this during high-frequency drive, as a result of electromagnetic waves leaking from a wiring section connected to the photoelectric conversion element.
Therefore, no effective proposal currently exist for easily and inexpensively manufacturing an optical element having superior optical characteristics and capable of supporting high-speed communication with a small number of components.